Improve `matrix` object

Since it basically has the same properties that the `block-list` objects we can make proper use of the DRY principle and @extend it.
Add missing 'lap-and-up' and 'desk-wide' to 'hide' helper classes
Remove trailing whitespace.
Updated inuit.css documentation link in README
Merge pull request #142 from kamilogorek/patch-1

Updated inuit.css documentation link in README
Update inuit.css/generic/_widths.scss

just fix a little misspelling
Merge pull request #143 from aastudio/patch-1

Fix typo in comment
Merge pull request #141 from javierav/whitespace

Remove trailing whitespace
Merge pull request #130 from bewildergeist/fix/hide-helpers

Add missing 'lap-and-up' and 'desk-wide' to 'hide' helper classes
Add float none helper
Add text helper comment
Add margin and padding helpers
Improve go class
Improve hidden content helper
Merge remote-tracking branch 'kevva/fix/matrix' into fix/matrix

Fixes #112
Add !important flags to helpers
Wrap hidden elements CSS up in a mixin
[refs #94] Reinstate links’ initial underline
[refs #94] Remove links module altogether
Merge remote-tracking branch 'waynemoir/master' into tkt-150